1. Field of the Invention
The present invention relates to an inverter control apparatus that drives an induction motor without using a position sensor and a velocity sensor.
2. Discussion of the Background
As an inverter control apparatus that drives an induction motor without using a velocity sensor, there is known a method using a flux observer as a state estimator. The difference between an estimated current estimated by the state estimator and an actual current is obtained, and the integral quantity of the scalar product of this difference and the estimated current is used as a temperature change amount.
For example, Japanese Unexamined Patent Application Publication No. 2005-20817 discloses that, during operation of an induction motor, the integral quantity of a scalar product is obtained, and a primary resistance value used in a state estimator is corrected, thereby performing a high-performance operation.
In the control apparatus, first, a set constant concerning temperature change in an arithmetic expression of the state estimator is directly changed by using a temperature change amount obtained during operation of the induction motor. Thus, calculation becomes complicated. In addition, it is difficult to take into consideration noise component removal, addition of a limiter, and the like.
Second, in calculation of the scalar product of an estimated current and a detected current that are two-phase alternating current signals, a phase difference occurs between the both signals due to a delay of detection timing of current, a delay of estimation calculation, and the like. Thus, a temperature change amount becomes different from the true value, and deterioration of control cannot be suppressed.
Third, at a regeneration state of the motor, a compensation direction needs to be inverted, but it is not taken into consideration.
An object of the invention is to provide: an inverter control apparatus that suppresses deterioration of control, which is caused by a temperature change and a setting error of a constant for a motor, and achieves stable drive of the motor; and a control method thereof.